1. Field of the Disclosure
The present disclosure relates to an acceleration shock reduction apparatus for vehicles that may be driven by power transmitted from a prime mover such (e.g., an internal combustion engine, etc.) to wheels via a transmission. Furthermore, the present disclosure relates to an acceleration shock reduction apparatus wherein an output of the prime mover may be varied (e.g., dampened, modulated, etc.) from a requested demand input.
2. Description of the Related Art
With market demands for high performance vehicles, prime movers (e.g., internal combustion engines, electric motors, hybrid drives, etc.) having improved torque response to accelerator pedal manipulation are desirable. Thus, a variety of power trains capable of meeting demands for improved torque response have been proposed.
Assignees of the present disclosure have also proposed an internal combustion engine including a variable valve mechanism capable of regulating engine intake by controlling an operation angle and a lift amount of an intake valve to achieve improved torque response characteristics.
When a transmission system, (i.e., a series of mechanisms for transmitting power from the prime mover to the wheels) is in a non-rigid coupling state, the transmission system operates as follows upon manipulating the prime mover from an unloaded state provided by releasing an accelerator pedal to a loaded state provided by depressing the accelerator pedal.
When torque transfer characteristics of the engaging element (e.g., torque transfer capacities of the engaging element) are abruptly changed during an engagement process of the engaging element, acceleration shock may occur in connection with acceleration resulting from depressing the accelerator pedal. In a vehicle having a prime mover exhibiting excellent torque response characteristics as described above, the acceleration shock may be substantial due to the high torque response of the prime mover.
Here, the term “non-rigid coupling state” refers to a state wherein the engaging element such as a clutch or a brake, is not completely engaged. “Non-rigid coupling state” may also refer to a state when the engaging element is completely engaged, but another engaging element, such as a one-way clutch, a lock-up clutch of a torque converter, or a friction clutch of a manual transmission is not completely engaged.
In order to reduce the acceleration shock, an inverse filter as disclosed in Japanese Patent Laid-open Publication No. 2004-150388 proposes an inverse filtering (flattening treatment) of an engine demand torque provided by manipulation of the accelerator pedal to perform phase delay correction of the engine demand torque, thus relieving the rapid torque variation.
As the rapid variation of the engine demand torque is decreased, the variation in actual engine output torque is also decreased and the increase in engine RPM is suppressed by such an amount during completion of the engagement process of the engaging element in the transmission system disposed in the non-rigid coupling state between the engine and the wheels upon acceleration, thereby reducing the acceleration shock.
Conventional techniques merely decreases the variation of the engine demand torque by inverse filtering (i.e., a flattening treatment) of the engine demand torque. However, when inverse filtering is performed exceedingly, torque response characteristics (i.e., acceleration response) deteriorate until the engaging element is completely engaged, thereby resulting in reduced acceleration performance. In contrast, when inverse filtering (flattening treatment) is performed insufficiently, the amount of acceleration shock reduction is insufficient upon completion of the engagement process of the engaging element. Therefore, conventional techniques have difficulty achieving an optimal balance between acceleration shock reduction and a desired amount of acceleration response.